Fusible electric circuit breaking device



Jam. 12, 1937. K. NOBUHARA FUSIBLE ELECTRIC CIRCUIT BREAKING DEVICEPatented Jan. 12, 1937 UNITED :STATES FUSIBLE ELECTRIC CIRCUIT BREAKINGY DEVICE Kantaro Nobuhara; Osaka, Japan Application October 1, 1934,Serial No. 146,432

f In Japan October 10, 1933 2 Claims. (Cl; 200-'120) This inventionrelates to improvements in a fusible electric circuit-breaking device tobe used for high-tension transmission lines. It consists of a pluralityof thin flat plates made of a noncombustible and insulating material,each plate having a small hole at its center, a fusible wire threadedthrough said holes so that the said plates are aligned in contact witheach other along their fiat surfaces, and a means to quickly pull outthe fusible wire from the holes when the wire is melted at any portionthereof.

The object of this invention is to obtain a fusible electriccircuit-breaking device for high-tension lines, wherein the gas producedwhen the fusible wire is melted diffuses quickly through the radialpassages in the shell in order to cool the gas quickly and to ensureonly a small cross-sectional area of the gas along an avenue of escape,whereby the interruption of the circuit is performed quickly and withoutturbulence.

A further object of this invention is to obtain a fusible electriccircuit-breaking device for hightension lines, wherein the fusible wireextending through a non-combustible insulating shell having a number ofpassages for gas therein perpendicular to the passage of the wire iswithdrawn from the shell when the wire is melted at any point in theshell.

A further object of this invention is to obtain a fusible electriccircuit-breaking device for hightension lines, wherein the fusible wireextending through a non-combustible insulating shell having a number ofpassages for gas therein perpendicular to the passage of the wire ismade of reduced cross-sectional area at one part, so that the wire isalways melted at a predetermined point in the shell.

Fig. 1 shows an elevation of a preferred form of the circuit-breakingdevice according to this invention, illustrating the device at themoment when the wire is melted and the gas is blowing out through thepassages adjacent the point of break.

Fig. 2 shows a sectional elevation of a modification, and Fig. 3 is anelevation of another example of this invention.

In Fig. 1, the high-tension line I is supported by insulators 2 in whichis inserted a circuitbreaking device. The device consists of a fusiblewire 3 extended between terminals 4 fixed on the insulators and anon-combustible insulating shell 5 through which the wire extends. Theshell consists of a number of thin plates made of porcelain or likematerial having a small hole perforated axially through the center ofeach plate, the plates being aligned in tubular form.

If the fusible wire 3 is melted at any point in the shell 5, the hightemperature gas produced by the melting wire is blown out radiallythrough the increased clearances between the plates adjacent to thepoint of break (compressive stress on said plates being released uponbreak in the wire), leaving only a small quantity of the gas in the holefor the wire, so that the electro-conducting effect of the gas in thedirection of the line is very small. Moreover, since the heat-absorbingcapacity of a solid material such as porcelain is surprisingly large ascompared to that of air (heat absorbing capacity is proportional to thespecific gravity) and since a large cooling surface is provided by theplurality of plates, the heat of the gas passing through the passages isquickly absorbed by the plates so that the gas is cooled rapidly and itselectro-conductivity is lowered.

In the modification shown in Fig. 2, a disc 6 having a larger diameteris inserted at intervals of a certain number of small discs I, and thediameter of the fusible wire is reduced at the centre part 8. Theterminal parts are made of a material having a good conductivity and areshown as having the shape of a ring 9.

Instead of reducing the diameter of the wire at some point along itslength, the wire may be made of different materials having differentelectro-specific resistances, the material of highest resistance beingarranged at the centre part thereof. According to this modification, thewire is always fused and breaks at the centre part.

The discs 6, having a larger diameter, serve to prevent the passage ofsurface leakage current.

Referring to Fig. 3, the circuit-breaking device is arranged betweeninsulators co-operating with a tensioning device.

The ring 9 provided at each end of the fusible wire of Fig. 2 is hung ona hook ID of a rod H or l2 made of spring metal and shown as fast on aninsulator. One or both of the rods is shown as accompanied by atensioning device. This device serves to tension the fusible wire sothat when the wire breaks, it is quickly withdrawn from the shell.

The tensioning device may be of any type. The example shown in Fig. 3consists of an external case l3 heldon an insulator having a spindle Mwhich tends to turn quickly in the direction shown by an arrow, by meansof a strong spring, not shown, provided in the case. A cushion plate I5is provided on the case, which serves to receive gently the rod H, whichlatter is shown as mounted on the spindle I, when the rod is turned backquickly by means of the tensioning device. The positions of the rodswhen the wire has broken are shown in dotted lines.

In case the fusible wire is melted, the rod I2 is quickly withdrawn,withdrawing a part of the wire from the shell, until it rests on thecushion plate. At the moment when the wire is fused, the gas which isproduced spreads radially in the gaps between the discs of the shell asbeforementioned, and the parts of the broken wire are withdrawn throughthe shell at high speed, so that an electric arc cannot follow thebroken ends of the wire which are being withdrawn.

The device can be arranged in an oil bath as well as in air.

What I claim is 1. A circuit-breaking device for high-tension lines,comprising a fusible wire, and a plurality of thin flat plates separatefrom each other and made of an incombustible and insulating material,each plate having a small hole at its center, said wire being threadedthrough said holes, and said plates being aligned in contact with eachother along their flat surfaces.

2. A circuit-breaking device for high-tension lines, comprising afusible wire, and a plurality of thin flat plates separate from eachother and made of an incombustible and insulating material, each platehaving a small hole at its center, said wire being threaded through saidholes, said plates being aligned in contact with each other along theirflat surfaces, and additional thin plates, of larger dimensions thansaid first-mentioned plates, interposed at regular intervals betweengroups of a predetermined number of said first-mentioned plates.

KANTARO NOBUHARA.

